Habitat loss, a leading threat to wildlife, is expected to escalate under global climate change resulting in the extinction of many species. Climate change is likely to raise sea levels by 0.18 m to 2 m over the next century, threatening many low-lying coastal areas such as the mid-Atlantic shoreline. Seavey et al. (2010) assessed the threat of sea-level rise (SLR) on the federally threatened piping plover (Charadrius melodus) on the barrier islands of Suffolk County, New York. The authors determined the extent of habitat change over the next 100 years under several SLR predictions. The results illustrate that if plover habitat cannot migrate, SLR is likely to reduce breeding areas. However, if habitat is able to migrate upslope and inland, breeding areas could actually increase. Unfortunately, this potential habitat gain is stymied by human development, which was found to reduce migrating habitat by 5–12%. The migration of potential habitat area was inhibited mostly by the spatial configuration of developed areas rather than the intensity of development. If the relative amount of plover habitat increases, human-plover conflict will likely arise as well. Finally, a large hurricane could flood up to 95% of plover habitat, thereby highlighting the risk from the synergism between SLR and coastal storms. To assure the future of plover habitat on these barrier islands, the authors assert that management needs to promote natural overwash and habitat migration, while minimizing development adjacent to future breeding habitat.—Michelle Schulte
Seavey, J.R., Gilmer, B., McGarigal, K.M., 2010. Effect of sea-level rise on piping plover (Charadrius melodus) breeding habitat. Biological Conservation 144, 393–401.
To study the potential change in piping plover breeding habitat with rising sea levels, the authors analyzed the barrier island system of Suffolk County, which spans 93 km of barrier island and peninsula shoreline along the southern coast of Long Island, New York. Multiple inlets break this barrier system into four segments. The islands are approximately 6 km by 0.1 km for the smallest and 50 km by 2.6 km for the largest. These dimensions are not stable, as island profiles are shifting and dynamic. The elevation of these islands is almost entirely below 3.5 m. Human development within the system is highly variable. Seavey et al. modeled two possible responses of plover habitat to SLR: static and dynamic. In the static habitat response, it was assumed that SLR would occur at a rate that outpaces the migration of habitat and the islands themselves. In this model, the spatial distribution of habitat was fixed and the rising sea level simply submerged land and existing habitat, resulting in a new spatial configuration of remaining habitat. A static habitat response is expected if the rate of SLR outpaces the ability of flora and fauna to migrate upslope and/or if development blocks movement of the landform. The second response model allowed for a dynamic habitat response wherein habitat could shift upslope and inland, redistributing itself based on the underlying landform. This habitat response was based on a plovar breeding habitat map created previously.
Using a global positioning system, the authors delineated the inland habitat boundary based on the presence of dense vegetation, steeply eroded banks, or human-made structures along the entire barrier island coastline of Suffolk County. The ocean-side habitat boundary was delineated as the high water line. The final format of this habitat map was an ESRI raster grid with 5 m horizontal resolution. This grid served as the base map for the analysis of the static habitat response and the binary response variable in a logistic generalized linear model (GLM) used to predict plover breeding habitat under the dynamic habitat response. Four well-supported SLR scenarios were chosen to model habitat changes. Each scenario represented a 30-year average SLR prediction, centered on 2080. Three of the four SLR scenarios are based on Intergovernmental Panel on Climate Change (IPCC) and New York City Panel on Climate Change estimates. The scenarios are B1 (0.38 m rise). A1B (0.47 m rise), and A2 (0.5 m rise). The fourth SLR scenario was based on recently verified rates of ice sheet loss and it stipulated a SLR of 1.5 m, higher than IPCC predictions. The four SLR scenarios, plus no SLR, were applied to both the static and dynamic habitat response models.
In addition, development data including buildings, roads, jetties and groins were digitized to create a development intensity surface. The authors wanted to compare the influence of development on the dynamic habitat response models by systematically examining each SLR scenario under various levels of development intensity. Next, Seavey et al. examined the risk of storm-induced plover habitat flooding under the 1.5 m SLR. Three types of storms were used: 5-year storm surge average (1.65 m), category-two hurricanes (0–2.4 m), and category- three hurricanes (0–3.7 m). The amount of plover habitat flooded by each storm type was calculated by clipping the resulting 1.5 m dynamic SLR with development habitat map by each storm flood extent.
The response of the barrier island plover habitat to SLR (i.e., static versus dynamic response) can make a large difference in predictions of future habitat. Habitat migration allowed for an increase in plover habitat with SLR in Suffolk County, New York. This increase resulted from the specific topography of these particular islands, which has more land area at higher elevations and inland compared to the current position of plover habitat. However, the ability of plover habitat to migrate across this particular landscape is uncertain and complex. Without considering the influence of development, the pattern of habitat change under increasing SLR differed greatly between the static and dynamic habitat response models. Potential piping plover breeding habitat area was reduced by as much as 41% under the static response model. In contrast, in the dynamic model habitat area grew by as much as 15%. This increase in relative amount of habitat reflected the steady loss of the barrier island system in this model. Under the dynamic response, the study area was also lost due to flooding; however, the habitat redistributed itself across the landscape in greater proportion. As the SLR estimate increased, the amount of plover habitat went from 32% to 65% of the total barrier island system. Furthermore, the authors assert that the future of plover habitat with rising sea levels will be dictated, in large part, by how coastal development is zoned and managed.
Regardless of the migration response, SLR in combination with the predicted increase in storminess due to climate change is likely to increase nest failure. Storm surge flooding impacted a large proportion of the projected habitat under the 1.5 m SLR with development scenario. The 5-year storm and category-two hurricane surge flooded about 75% of potential nesting habitat; whereas a category-three hurricane surge flooded over 95% of the area. Among the piping plover nests found in the study area during the 2003–2005 breeding seasons, 74% of nests would have been flooded by a 5-year storm, 73% by a category-two hurricane, and 97% by a category-three hurricane. The large impact from all storm types stemmed from the relatively low elevation of the barrier island system in Suffolk County. While it is uncertain what the loss of one breeding season would mean to the overall plover population, the increased frequency of large storms predicted to accompany global climate change may make nest flooding more frequent and likely to increase population risk.
Their results raise concern over the potential for SLR to increase human-plover conflict. Both habitat response models predict an increase in the proportion of the island areas in potential plover habitat over the next 100 years. If the relative amount of plover habitat increases, conflict is likely to arise especially as the human population in the region grows. Moreover, interspecies competition for nesting space and other resources may increase as plovers, American oystercatchers (Haematopus palliatus), least terns (Sternula antillarum), common terns (Sterna hirundo), and other coastal species are crowded together.
Habitat loss resulting from SLR, especially along low-lying, developed coastlines, is likely to increase piping plover extinction risk. To avoid the potential loss of plover habitat, management actions must be based on the assumption that coasts are dynamic, highly variable, and will shift with rising sea levels. Today’s plover nesting habitat is unlikely to be suitable, or even exist, in the near future. Management will need to be adaptive and focus on actions that restrict and even reduce development so that ecological processes, such as overwash and habitat migration, are preserved.